Search Results

The EPAct/V2/E-89 gasoline fuel effects program collected emissions data for 27 test fuels using a fleet of 15 high-sales cars and light trucks from the 2008 model year (all with port fuel injection). The test fuel matrix covered values of T50, T90, vapor pressure, ethanol content, and total aromatic content spanning ranges typical of market gasolines. Emission measurements were made over the LA92 cycle at a nominal temperature of 24°C (75°F). The resulting emissions database of 956 tests includes a particulate matter (PM) mass measurement for each. Emission models for PM fuel effects were fit based on terms for which the fuel matrix was originally optimized, with results published by EPA in a 2013 analysis report. This paper presents results of a subsequent modeling analysis of this PM data using the PM Index fuel parameter, and compares these models to the original versions.

A pilot study was performed to explore the effects of PM Index, low and high molecular weight aromatics, and ethanol content on particulate matter (PM) emissions from light-duty Tier 2 gasoline vehicles. Four test vehicles from model years 2007-2009 were tested on seven fuels spanning PM Index values from 0.9 to 2.7, aromatic content from 14 to 38%, and ethanol content from 0 to 15%. Three of the test vehicles were port fuel injected (PFI) while the fourth featured gasoline direct injection (GDI). In an earlier program, two of the PFI vehicles demonstrated high sensitivity of PM emissions to fuel property changes while the third showed low sensitivity. The sensitivity of the GDI vehicle to fuel property changes was not known prior to this study. The vehicles were tested over the LA92 and US06 test cycles at 24°C (75°F). PM and regulated gaseous emissions were measured by test phase. Second-by-second tailpipe soot emissions were measured using the AVL Micro Soot Sensor.

A series of paired fuel tests were conducted comparing certification-grade highway diesel fuel with 5 to 50 vol% soy-methyl-ester biodiesel blends. Each fuel pair was tested for up to seven transient cycles representing various load conditions, using a 2006 model year Cummins ISB compression ignition engine equipped with exhaust gas recirculation. Except for the most lightly-loaded cycle, the results show statistically significant differences in NOx emission for all fuel pairs. The average NOx emissions due to biodiesel increased over each cycle, ranging from 0.9 to 6.6% and from 2.2 to 17.2% for the B20/B0 and B50/B0 fuel pairs, respectively. Significant reductions in CO and PM were observed over a majority of the cycles tested. The data also reveal that the change in NOx emissions increases linearly with the average cycle load. To complement the transient results, a single modal point was monitored daily to investigate biodiesel effects on engine operating parameters.

The U.S. Environmental Protection Agency (EPA) formed a Heavy-Duty Engine Working Group (HDEWG) in the Mobile Sources Technical Advisory Subcommittee in 1995. The goal of the HDEWG was to help define the role of the fuel in meeting the future emissions standards in advanced technology engines (beyond 2004 regulated emissions levels). A three-phase program was developed. This paper presents the results of the statistical analysis of the data collected in the Phase II program. Included is a description of the design of the fuel test matrix, and a listing of the regression equations developed to predict emissions as a function of fuel density, cetane number, monoaromatics, and polyaromatics. Also included is a description of selected analyses of the emissions from a smaller set of fuel data that allowed direct comparison of the effects of natural and boosted cetane number.

In 1995, US Environmental Protection Agency (EPA) formed the Heavy-Duty Engine Working Group (HDEWG). The objective of the group was to assess the role diesel fuel could play in meeting exhaust emission standards proposed for model year 2004+ heavy-duty diesel engines. The group developed a three-phase program to achieve this objective. This paper describes the development of test fuels used in Phase 2 of the EPA HDEWG Program to investigate the effect of fuel properties on heavy-duty diesel engine emissions. It discusses the design of the fuel matrix, reviews the process of test fuel preparation and presents the results of a multi-laboratory fuel analysis program. Fuel properties selected for investigation included density, cetane number, mono- and polyaromatic hydrocarbon content.

In 1997 the US EPA formed a Heavy-Duty Engine Working Group (HDEWG) in the Mobile Sources Technical Advisory Subcommittee to address the questions related to fuel property effects on heavy-duty diesel engine emissions. The Working Group consisted of members from EPA and the oil refining and engine manufacturing industries. The goal of the Working Group was to help define the role of the fuel in meeting the future emissions standards in advanced technology engines (beyond 2004 regulated emissions levels). To meet this objective a three-phase program was developed. Phase I was designed to demonstrate that a prototype engine, located at Southwest Research Institute, represented similar emissions characteristics to that of certain manufacturers prototype engines. Phase II was designed to document the effects of selected fuel properties using a statistically designed fuel matrix in which cetane number, density, and aromatic content and type were the independent variables.

A study of cetane response of post-1993 U.S. No. 2 diesel fuels was performed following the October 1, 1993 introduction of the federally mandated 0.05% sulfur, on-highway diesel fuel. Seven fuels obtained from East Coast, Gulf Coast and Midwest refineries, an emissions certification fuel and a low aromatic California fuel were evaluated. Ethylhexyl nitrate was used as cetane improver in concentrations of up to 1 vol.%. Test results demonstrated relatively low cetane response of non-California fuels and an exceptionally high response of the low aromatic California fuel. The only predictive cetane response equation available in technical literature failed to accurately characterize the performance of fuels used in this study. An inter-industry program is proposed to (a) develop a detailed understanding of diesel fuel composition/property effects on cetane response and (b) define an improved cetane response equation applicable to the full range of diesel fuels.

A production, direct injection diesel engine was modified to incorporate BP Oil's novel variable compression ratio (VCR) engine concept. The operation of the VCR mechanism was demonstrated and the performance and emissions potential of the concept evaluated. The VCR prototype achieved twice the specific power output of the baseline turbocharged, aftercooled engine. Its exhaust smoke emissions at high load were consistent with conventional direct injection (DI) diesel engines using equivalent fuel injection equipment. Light load particulate emissions and high load fuel consumption indicated a need for further development of the combustion system. Unexpectedly low HC emissions were achieved considering the large crevice volumes in the combustion chamber of the prototype engine. Likewise, exceptionally low NOx emissions were demonstrated. It is believed that the low HC and NOx emissions could be inherent features of the unique combustion system configuration.